Grammatical Impairments in PPA

Speech-language within and between network disruptions in primary progressive aphasia variants

Primary progressive aphasia (PPA) variants present with distinct disruptions in speech-language functions with little known about the interplay between affected and spared regions within the speech-language network and their interaction with other functional networks. The Neurodegenerative Research Group, Mayo Clinic, recruited 123 patients with PPA (55 logopenic (lvPPA), 44 non-fluent (nfvPPA) and 24 semantic (svPPA)) who were matched to 60 healthy controls. We investigated functional connectivity disruptions between regions within the left-speech-language network (Broca, Wernicke, anterior middle temporal gyrus (aMTG), supplementary motor area (SMA), planum temporale (PT) and parietal operculum (PO)), and disruptions to other networks (visual association, dorsal-attention, frontoparietal and default mode networks (DMN)). Within the speech-language network, multivariate linear regression models showed reduced aMTG-Broca connectivity in all variants, with lvPPA and nfvPPA findings remaining significant after Bonferroni correction. Additional loss in Wernicke-Broca connectivity in nfvPPA, Wernicke-PT connectivity in lvPPA and greater aMTG-PT connectivity in svPPA were also noted. Between-network connectivity findings in all variants showed reduced aMTG-DMN and increased aMTG-dorsal-attention connectivity, with additional disruptions between aMTG-visual association in both lvPPA and svPPA, aMTG-frontoparietal in lvPPA, and Wernicke-DMN breakdown in svPPA. These findings suggest that aMTG connectivity breakdown is a shared feature in all PPA variants, with lvPPA showing more extensive connectivity disruptions with other networks.

Discriminating nonfluent/agrammatic and logopenic PPA variants with automatically extracted morphosyntactic measures from connected speech

Morphosyntactic assessments are important for characterizing individuals with nonfluent/agrammatic variant primary progressive aphasia (nfvPPA). Yet, standard tests are subject to examiner bias and often fail to differentiate between nfvPPA and logopenic variant PPA (lvPPA). Moreover, relevant neural signatures remain underexplored. Here, we leverage natural language processing tools to automatically capture morphosyntactic disturbances and their neuroanatomical correlates in 35 individuals with nfvPPA relative to 10 healthy controls (HC) and 26 individuals with lvPPA. Participants described a picture, and ensuing transcripts were analyzed via part-of-speech tagging to extract sentence-related features (e.g., subordinating and coordinating conjunctions), verbal-related features (e.g., tense markers), and nominal-related features (e.g., subjective and possessive pronouns). Gradient boosting machines were used to classify between groups using all features. We identified the most discriminant morphosyntactic marker via a feature importance algorithm and examined its neural correlates via voxel-based morphometry. Individuals with nfvPPA produced fewer morphosyntactic elements than the other two groups. Such features robustly discriminated them from both individuals with lvPPA and HCs with an AUC of .95 and .82, respectively. The most discriminatory feature corresponded to subordinating conjunctions was correlated with cortical atrophy within the left posterior inferior frontal gyrus across groups (pFWE < .05). Automated morphosyntactic analysis can efficiently differentiate nfvPPA from lvPPA. Also, the most sensitive morphosyntactic markers correlate with a core atrophy region of nfvPPA. Our approach, thus, can contribute to a key challenge in PPA diagnosis.

Patterns of performance on the animal fluency task in logopenic variant of primary progressive aphasia: A reflection of phonological and semantic skills

PURPOSE

This study aimed to characterize the quantitative (total number of correct words generated) and qualitative (psycholinguistic properties of correct words generated) performance patterns on the animal fluency task in individuals with the logopenic variant of primary progressive aphasia and to investigate the influence of phonological and semantic abilities to these patterns.

METHODS

Fifteen participants with lvPPA and twenty neurotypical adults completed the animal fluency task and an assessment battery to characterize their phonological and semantic abilities. We recorded the total number of correct words produced and their psycholinguistic properties. Group differences were analyzed using independent samples t-tests and analysis of covariance. Stepwise and multiple linear regression analyses were implemented to investigate the contribution of psycholinguistic properties on word generation as well as the role of phonological and semantic abilities on performance. We also investigated the mediating role of phonological and semantic abilities on the relationship between relevant psycholinguistic properties and word generation output.

RESULTS

Compared to neurotypical controls, participants with lvPPA produced fewer correct responses and more words with lower age of acquisition. The total number of correct words generated was predicted by the age of word acquisition, such that individuals who generated more responses, produced words acquired later in life. Phonology and semantics influenced the number of correct words generated and their frequency, age of acquisition, and semantic neighborhood density. Familiarity and arousal were driven by semantic abilities. Phonological abilities partially mediated the relationship between age of acquisition and word generation output.

CONCLUSIONS

This study provides valuable insights into the performance patterns of the animal fluency task in lvPPA. Individuals with lvPPA with more intact phonological and semantic abilities generated greater number of words with more complex psycholinguistic properties. Our findings contribute to the understanding of language processes underlying word retrieval in lvPPA.

The production of adjectives in narratives by individuals with primary progressive aphasia

Adjectives (e.g., hungry) are an important part of language, but have been little studied in individuals with impaired language. Adjectives are used in two different ways in English: attributively, to modify a noun (the hungry dog); or predicatively, after a verb (the dog is hungry). Attributive adjectives have a more complex grammatical structure than predicative adjectives, and may therefore be particularly prone to disruption in individuals with grammatical impairments. We investigated adjective production in three subtypes of primary progressive aphasia (PPA: agrammatic, semantic, logopenic), as well as in agrammatic stroke aphasia and a group of healthy control participants. Participants produced narratives based on picture books, and we coded every adjective they produced for its syntactic structure. Compared to healthy controls, the two agrammatic groups, but not the other two patient groups, produced significantly fewer attributive adjectives per sentence. All four patient groups were similar to controls for their rate of predicative adjective production. In addition, we found a significant correlation in the agrammatic PPA participants between their rate of producing attributive adjective and impaired production of sentences with complex syntactic structure (subject cleft sentences like It was the boy that chased the girl); no such correlation was found for predicative adjectives. Irrespective of structure, we examined the lexical characteristics of the adjectives that were produced, including length, frequency, semantic diversity and neighborhood density. Overall, the lexical characteristics of the produced adjectives were largely consistent with the language profile of each group. In sum, the results suggest that attributive adjectives present a particular challenge for individuals with agrammatic language production, and add a new dimension to the description of agrammatism. Our results further suggest that attributive adjectives may be a fruitful target for improved treatment and recovery of agrammatic language.

Neural mechanisms of sentence production: a volumetric study of primary progressive aphasia

Studies on the neural bases of sentence production have yielded mixed results, partly due to differences in tasks and participant types. In this study, 101 individuals with primary progressive aphasia (PPA) were evaluated using a test that required spoken production following an auditory prime (Northwestern Assessment of Verbs and Sentences-Sentence Production Priming Test, NAVS-SPPT), and one that required building a sentence by ordering word cards (Northwestern Anagram Test, NAT). Voxel-Based Morphometry revealed that gray matter (GM) volume in left inferior/middle frontal gyri (L IFG/MFG) was associated with sentence production accuracy on both tasks, more so for complex sentences, whereas, GM volume in left posterior temporal regions was exclusively associated with NAVS-SPPT performance and predicted by performance on a Digit Span Forward (DSF) task. Verb retrieval deficits partly mediated the relationship between L IFG/MFG and performance on the NAVS-SPPT. These findings underscore the importance of L IFG/MFG for sentence production and suggest that this relationship is partly accounted for by verb retrieval deficits, but not phonological loop integrity. In contrast, it is possible that the posterior temporal cortex is associated with auditory short-term memory ability, to the extent that DSF performance is a valid measure of this in aphasia.

Using Generative Artificial Intelligence to Classify Primary Progressive Aphasia from Connected Speech

Neurodegenerative dementia syndromes, such as Primary Progressive Aphasias (PPA), have traditionally been diagnosed based in part on verbal and nonverbal cognitive profiles. Debate continues about whether PPA is best subdivided into three variants and also regarding the most distinctive linguistic features for classifying PPA variants. In this study, we harnessed the capabilities of artificial intelligence (AI) and natural language processing (NLP) to first perform unsupervised classification of concise, connected speech samples from 78 PPA patients. Large Language Models discerned three distinct PPA clusters, with 88.5% agreement with independent clinical diagnoses. Patterns of cortical atrophy of three data-driven clusters corresponded to the localization in the clinical diagnostic criteria. We then used NLP to identify linguistic features that best dissociate the three PPA variants. Seventeen features emerged as most valuable for this purpose, including the observation that separating verbs into high and low-frequency types significantly improves classification accuracy. Using these linguistic features derived from the analysis of brief connected speech samples, we developed a classifier that achieved 97.9% accuracy in predicting PPA subtypes and healthy controls. Our findings provide pivotal insights for refining early-stage dementia diagnosis, deepening our understanding of the characteristics of these neurodegenerative phenotypes and the neurobiology of language processing, and enhancing diagnostic evaluation accuracy.

Characterization of the logopenic variant of Primary Progressive Aphasia: A systematic review and meta-analysis

The linguistic and anatomical variability of the logopenic variant of Primary Progressive Aphasia (lv-PPA) as defined by current diagnostic criteria has been the topic of an intense debate. The present review and meta-analysis aims at characterizing the profile of lv-PPA, by a comprehensive analysis of the available literature on the neuropsychological, neuroimaging, electrophysiological, pathological, and genetic features of lv-PPA. We conducted a systematic bibliographic search, leading to the inclusion of 207 papers. Of them, 12 were used for the Anatomical Likelihood Estimation meta-analysis on grey matter revealed by magnetic resonance imaging data. The results suggest that the current guidelines outline a relatively consistent syndrome, characterized by a core set of linguistic and, to a lesser extent, non-linguistic deficits, mirroring the involvement of left temporal and parietal regions typically affected by Alzheimer Disease pathology. Variations of the lv-PPA profile are discussed in terms of heterogeneity of the neuropsychological instruments and the diagnostic criteria adopted.

Verb Frequency and Density Drive Naming Performance in Primary Progressive Aphasia

Background

Recent work has highlighted the utility of the Boston Naming Test and Hopkins Action Naming Assessment (HANA) for distinguishing between semantic (svPPA), logopenic (lvPPA) and non-fluent agrammatic (nfavPPA) variants of primary progressive aphasia (PPA).

Aims

To determine whether item level differences between variants on when naming verbs on the HANA were able to be accounted for using common variables of lexical interest: word frequency, semantic density, concreteness, or valency. We also examined three specific hypotheses: (1) svPPA and lvPPA may result in increased difficulty with decreased semantic density compared to nfavPPA; (2) svPPA may result in increased difficulty with decreased concreteness; and (3) nfavPPA may result in increased difficulty with high syntactic valency.

Methods & Procedures

268 patients with PPA were evaluated using the HANA. A hierarchical Bayesian regression approach was adopted to account for effects of repeated measurement within participants and items.

Outcomes & Results

The main effects of variant and verb trait were significant in all models, as was the interaction for frequency, semantic density, and valency. Increasing frequency, semantic density, and concreteness led to better performance, while increasing valency led to poorer performance. Low semantic density contributed to greater difficulty in svPPA and lvPPA, but low concreteness did not uniquely impact verb naming in svPPA. Those with nfavPPA had no particular difficulty as a result of valency.

Conclusions

Prior studies have identified the independent effects of frequency and semantic density on verb naming in PPA, which were confirmed by our analyses, and the best predictions of the data were achieved by combining these dimensions. This investigation complements our previous work highlighting the value of the HANA for efficiently demonstrating verb performance in PPA.

A syntax-lexicon trade-off in language production

Spoken language production involves selecting and assembling words and syntactic structures to convey one's message. Here we probe this process by analyzing natural language productions of individuals with primary progressive aphasia (PPA) and healthy individuals. Based on prior neuropsychological observations, we hypothesize that patients who have difficulty producing complex syntax might choose semantically richer words to make their meaning clear, whereas patients with lexicosemantic deficits may choose more complex syntax. To evaluate this hypothesis, we first introduce a frequency-based method for characterizing the syntactic complexity of naturally produced utterances. We then show that lexical and syntactic complexity, as measured by their frequencies, are negatively correlated in a large (n = 79) PPA population. We then show that this syntax-lexicon trade-off is also present in the utterances of healthy speakers (n = 99) taking part in a picture description task, suggesting that it may be a general property of the process by which humans turn thoughts into speech.

When words first fail: Predicting the emergence of primary progressive aphasia variants from unclassifiable anomic performance in early disease

Background

The majority of patients with primary progressive aphasia (PPA) can be distinguished into one of three variants: semantic, non-fluent/agrammatic, or logopenic. However, many do not meet criteria for any one variant.

Aim

To identify aspects of cognitive-linguistic performance that yield an early unclassifiable PPA designation that predicted the later emergence of a given variant.

Methods & Procedures

Of 256 individuals with PPA evaluated, 19 initially were unclassifiable and later met criteria for a variant. Receiver operating characteristic curves were used to evaluate the binary ability of a given task to predict eventual classification as a given variant. Tasks with a high area under the curve were examined using regression analyses to determine their ability to predict variant.

Outcomes & Results

High mean predictive value was observed for multiple naming assessments targeting nouns and verbs. The Boston Naming Test (BNT) was the only test that, in isolation, resulted in a significant model and high classification accuracy.

Conclusions

Although naming impairment is common across PPA variants, very low initial BNT scores emerged as a uniquely accurate basis for predicting eventual semantic variant, and normal BNT scores predicted eventual nonfluent/agrammatic variant. High performance on picture-verb verification was useful in identifying future lvPPA.

Sentence Comprehension in Primary Progressive Aphasia: A Study of the Application of the Brazilian Version of the Test for the Reception of Grammar (TROG2-Br)

Sentence-comprehension deficits have been described in patients with primary progressive aphasia (PPA). However, most instruments to address this domain in more detail and in a clinical context have not been adapted and translated into several languages, posing limitations to clinical practice and cross-language research.

Objectives

The study aimed to (1) test the applicability of the Brazilian version of the Test for Reception of Grammar (TROG2-Br) to detect morphosyntactic deficits in patients with PPA; (2) investigate the association between performance in the test and sociodemographic and clinical variables (age, years of formal education, and disease duration); (3) characterize the performance of individuals presenting with the three more common variants of PPA (non-fluent, semantic, and logopenic) and mixed PPA (PPA-Mx) and analyze whether TROG-2 may assist in the distinction of these clinical profiles.

Methods

A total of 74 cognitively healthy participants and 34 individuals diagnosed with PPA were assessed with TROG2-Br. Overall scores (correct items, passed blocks), types, and categories of errors were analyzed.

Results

In controls, block scores were significantly correlated with years of formal education (Spearman's r = 0.33, p = 004) but not with age. In PPA, age, education, and disease duration were not significantly associated with performance in the test. Controls presented a significantly higher performance on TROG2-Br compared to PPA individuals and their errors pattern pointed to mild general cognitive processing difficulties (attention, working memory). PPA error types pointed to processing and morphosyntactic deficits in nonfluent or agrammatic PPA, (PPA-NF/A), logopenic PPA (PPA-L), and PPA-Mx. The semantic PPA (PPA-S) subgroup was qualitatively more similar to controls (processing difficulties and lower percentage of morphosyntactic errors). TROG2-Br presented good internal consistency and concurrent validity.

Discussion

Our results corroborate findings with TROG-2 in other populations. The performance of typical older adults with heterogeneous levels of education is discussed along with recommendations for clinical use of the test and future directions of research.

Quantitative and Qualitative Differences of Action Verbal Fluency between Young and Older Adults

INTRODUCTION

Action verbal fluency (AVF) task, a word fluency test, involves language and executive function and is known to be sensitive to fronto-striatal degeneration. However, the ability may also decrease qualitatively as well as quantitatively in normal aging. The objective of this study is to investigate the age-related quantitative and qualitative differences in AVF of Korean adults.

METHODS

We analyzed data from 78 participants of 40 young (mean age = 28.9) and 38 older adults (mean age = 67.7). The correct responses in the AVF task were measured for quantitative analysis. Qualitatively, the mean number of arguments required by each verb was calculated for syntactic analysis. For semantic analysis, we subclassified verbs according to their characteristics (e.g., moment vs. non-moment verbs/active vs. non-active verbs) and calculated the ratio for comparison. The results of AVF were also compared to those of semantic/phonemic fluency and the Korean version of the Montreal Cognitive Assessment (MoCA-K).

RESULTS

The older group showed quantitatively lower performance in AVF than the young group (p < 0.01). The result of the AVF task significantly correlated (p < 0.01) with both semantic/phonemic fluency and the MoCA-K. Also, the older group produced syntactically more simple verbs than the counterpart (p < 0.01). In the semantic analysis, the older group produced fewer moment verbs (p < 0.05) but more non-moment verbs (p < 0.05) than the young group. There was no difference in active or non-active verbs between two groups.

CONCLUSION

These results indicated that the ability of AVF declines with age not only quantitatively but also qualitatively in relation to their cognitive changes.

Neuroanatomical correlations of visuospatial processing in primary progressive aphasia

Clinical phenotyping of primary progressive aphasia has largely focused on speech and language presentations, leaving other cognitive domains under-examined. This study investigated the diagnostic utility of visuospatial profiles and examined their neural basis among the three main primary progressive aphasia variants. We studied the neuropsychological performances of 118 primary progressive aphasia participants and 30 cognitively normal controls, across 11 measures of visuospatial cognition, and investigated their neural correlates via voxel-based morphometry analysis using visuospatial composite scores derived from principal component analysis. The principal component analysis identified three main factors: visuospatial-executive, visuospatial-memory and visuomotor components. Logopenic variant primary progressive aphasia performed significantly worst across all components; nonfluent/agrammatic variant primary progressive aphasia showed deficits in the visuospatial-executive and visuomotor components compared with controls; and the semantic variant primary progressive aphasia scored significantly lower than nonfluent/agrammatic variant primary progressive aphasia and control in the visuospatial-memory component. Grey matter volumes over the right parieto-occipital cortices correlated with visuospatial-executive performance; volumetric changes in the right anterior parahippocampal gyrus and amygdala were associated with visuospatial-memory function, and visuomotor composite scores correlated significantly with the grey matter volume at the right precentral gyrus. Discriminant function analysis identified three visuospatial measures: Visual Object and Space Perception and Benson figure copy and recall test, which classified 79.7% (94/118) of primary progressive aphasia into their specific variant. This study shows that each primary progressive aphasia variant also carries a distinctive visuospatial cognitive profile that corresponds with grey matter volumetric changes and in turn can be largely represented by their performance on the visuomotor, visuospatial-memory and executive functions.

Clinical and neuroimaging characteristics of primary progressive aphasia

The chapter covers the clinical syndrome of a primary progressive aphasia (PPA), the demographics of this rare neurodegenerative disease, defining clinical and neuroanatomic characteristics of each PPA variant, disease progression, and behavioral features. The chapter begins with a brief introduction that includes references to seminal papers that defined this clinical syndrome and its three variants. The classic PPA subtypes discussed in the chapter are semantic variant PPA (svPPA), nonfluent/agrammatic PPA (nfaPPA), and logopenic variant PPA (lvPPA). The key language and cognitive characteristics, and language tasks that can elicit these language impairments, are detailed. Overlap in the clinical profiles of the PPA variants, which make differential diagnosis challenging, are explained. Disease progression is described, revealing that the PPA variants become more similar over time. Although PPA is language-predominant dementia, there are behavioral manifestations, particularly in svPPA. Changes in behavior in this variant are addressed as well as behavioral changes in nfaPPA and lvPPA that are less well recognized. The patterns of atrophy in the left temporal, parietal, and/or frontal cortices unique to each PPA variant are described. The underlying neuropathologies of the PPA variants are discussed, specifically tauopathies and non-tauopathies associated with svPPA and nfaPPA and Alzheimer's disease pathology in lvPPA.

Task performance to discriminate among variants of primary progressive aphasia

Primary progressive aphasia can be distinguished into one of three variants: semantic, non-fluent/agrammatic, and logopenic. While a considerable body of work exists characterizing each variant, few prior studies have addressed the problem of optimizing behavioral assessment in a typical outpatient evaluation setting. Our aim is to examine the sensitivity and specificity of a battery of cognitive and linguistic assessments and determine optimal scores for distinguishing patients' subtype based on these instruments. This was a retrospective analysis of outpatient clinical testing of individuals with known or suspected primary progressive aphasia. Evaluations included the National Alzheimer's Coordinating Center frontotemporal lobar degeneration module and additional measures of naming, semantic association, word verification, and picture description. Receiver operating characteristic analysis was used to examine the utility of each task in distinguishing each variant from the others. Logistic regressions were used to examine the combined utility of tasks for distinguishing a given subtype. We examined 435 evaluations of 222 patients retrospectively. The battery was most consistent in distinguishing semantic variant by low scores and non-fluent/agrammatic variant by high scores on a similar subset of tasks. Tasks best distinguishing semantic variant produced a model that correctly classified 86% of cases. Tasks best distinguishing non-fluent/agrammatic variant correctly classified 77% of cases. The battery of tasks was weakest in identifying logopenic variant; only the ratio of sentence reading to sentence repetition performance was identified as a reasonable predictor, and it had predictive accuracy of 67%. Naming assessments were the strongest basis for distinguishing all variants, particularly semantic variant from non-fluent/agrammatic variant. These data illustrate that a number of commonly used assessments perform at chance in distinguishing variant and preliminarily support an abbreviated battery that marginally favors tools not currently included in the frontotemporal lobar degeneration module.

What Language Disorders Reveal About the Mechanisms of Morphological Processing

We addressed an understudied topic in the literature of language disorders, that is, processing of derivational morphology, a domain which requires integration of semantic and syntactic knowledge. Current psycholinguistic literature suggests that word processing involves morpheme recognition, which occurs immediately upon encountering a complex word. Subsequent processes take place in order to interpret the combination of stem and affix. We investigated the abilities of individuals with agrammatic (PPA-G) and logopenic (PPA-L) variants of primary progressive aphasia (PPA) and individuals with stroke-induced agrammatic aphasia (StrAg) to process pseudowords which violate either the syntactic (word class) rules (*reheavy) or the semantic compatibility (argument structure specifications of the base form) rules (*reswim). To this end, we quantified aspects of word knowledge and explored how the distinct deficits of the populations under investigation affect their performance. Thirty brain-damaged individuals and 10 healthy controls participated in a lexical decision task. We hypothesized that the two agrammatic groups (PPA-G and StrAg) would have difficulties detecting syntactic violations, while no difficulties were expected for PPA-L. Accuracy and Reaction Time (RT) patterns indicated: the PPA-L group made fewer errors but yielded slower RTs compared to the two agrammatic groups which did not differ from one another. Accuracy rates suggest that individuals with PPA-L distinguish *reheavy from *reswim, reflecting access to and differential processing of syntactic vs. semantic violations. In contrast, the two agrammatic groups do not distinguish between *reheavy and *reswim. The lack of difference stems from a particularly impaired performance in detecting syntactic violations, as they were equally unsuccessful at detecting *reheavy and *reswim. Reduced grammatical abilities assessed through language measures are a significant predictor for this performance, suggesting that the "hardware" to process syntactic information is impaired. Therefore, they can only judge violations semantically where both *reheavy and *reswim fail to pass as semantically ill-formed. This finding further suggests that impaired grammatical knowledge can affect word level processing as well. Results are in line with the psycholinguistic literature which postulates the existence of various stages in accessing complex pseudowords, highlighting the contribution of syntactic/grammatical knowledge. Further, it points to the worth of studying impaired language performance for informing normal language processes.

Identification of the main components of spontaneous speech in primary progressive aphasia and their neural underpinnings using multimodal MRI and FDG-PET imaging

BACKGROUND

Primary progressive aphasia (PPA) is a clinical syndrome characterized by gradual loss of language skills. This study aimed to evaluate the diagnostic capacity of a connected speech task for the diagnosis of PPA and its variants, to determine the main components of spontaneous speech, and to examine their neural correlates.

METHODS

A total of 118 participants (31 patients with nfvPPA, 11 with svPPA, 45 with lvPPA, and 31 healthy controls) were evaluated with the Cookie Theft picture description task and a comprehensive language assessment protocol. Patients also underwent ¹⁸F-fluorodeoxyglucose positron emission tomography and magnetic resonance imaging studies. Principal component analysis and machine learning were used to evaluate the main components of connected speech and the accuracy of connected speech parameters for diagnosing PPA. Voxel-based analyses were conducted to evaluate the correlation between spontaneous speech components and brain metabolism, brain volumes, and white matter microstructure.

RESULTS

Discrimination between patients with PPA and controls was 91.67%, with 77.78% discrimination between PPA variants. Parameters related to speech rate and lexical variables were the most discriminative for classification. Three main components were identified: lexical features, fluency, and syntax. The lexical component was associated with ventrolateral frontal regions, while the fluency component was associated with the medial superior prefrontal cortex. Number of pauses was more related with the left parietotemporal region, while pauses duration with the bilateral frontal lobe. The lexical component was correlated with several tracts in the language network (left frontal aslant tract, left superior longitudinal fasciculus I, II, and III, left arcuate fasciculus, and left uncinate fasciculus), and fluency was linked to the frontal aslant tract.

CONCLUSION

Spontaneous speech assessment is a useful, brief approach for the diagnosis of PPA and its variants. Neuroimaging correlates suggested a subspecialization within the left frontal lobe, with ventrolateral regions being more associated with lexical production and the medial superior prefrontal cortex with speech rate.

Automated analysis of lexical features in frontotemporal degeneration

We implemented an automated analysis of lexical aspects of semi-structured speech produced by healthy elderly controls (n = 37) and three patient groups with frontotemporal degeneration (FTD): behavioral variant FTD (n = 74), semantic variant primary progressive aphasia (svPPA, n = 42), and nonfluent/agrammatic PPA (naPPA, n = 22). Based on previous findings, we hypothesized that the three patient groups and controls would differ in the counts of part-of-speech (POS) categories and several lexical measures. With a natural language processing program, we automatically tagged POS categories of all words produced during a picture description task. We further counted the number of wh-words, and we rated nouns for abstractness, ambiguity, frequency, familiarity, and age of acquisition. We also computed the cross-entropy estimation, where low cross-entropy indicates high predictability, and lexical diversity for each description. We validated a subset of the POS data that were automatically tagged with the Google Universal POS scheme using gold-standard POS data tagged by a linguist, and we found that the POS categories from our automated methods were more than 90% accurate. For svPPA patients, we found fewer unique nouns than in naPPA and more pronouns and wh-words than in the other groups. We also found high abstractness, ambiguity, frequency, and familiarity for nouns and the lowest cross-entropy estimation among all groups. These measures were associated with cortical thinning in the left temporal lobe. In naPPA patients, we found increased speech errors and partial words compared to controls, and these impairments were associated with cortical thinning in the left middle frontal gyrus. bvFTD patients' adjective production was decreased compared to controls and was correlated with their apathy scores. Their adjective production was associated with cortical thinning in the dorsolateral frontal and orbitofrontal gyri. Our results demonstrate distinct language profiles in subgroups of FTD patients and validate our automated method of analyzing FTD patients' speech.

One cat, Two cats, Red cat, Blue cats: Eliciting morphemes from individuals with primary progressive aphasia

BACKGROUND

Progressive neurodegenerative impairment with central language features, primary progressive aphasia (PPA), can be further distinguished for many individuals into one of three variants: semantic, non-fluent/agrammatic, and logopenic variant PPA. Variants differ in their relative preservation and deficits of language skills, particularly in word finding and grammar. The majority of elicited language assessments used in this population focus on single noun and verb production, while modifiers and inflectional morphemes are far less commonly examined.

AIMS

The purpose of the present study is to determine whether there was an interaction between PPA variant and production of high-frequency nouns, proper names, modifiers, and bound inflectional morphemes to better understand how the variants differ.

METHODS & PROCEDURES

Forty-six people with PPA and 47 individuals with no known neurological diagnoses completed a morphosyntactic generation assessment designed to target differential production of high-frequency nouns, proper names, modifiers (number, size, color), and bound inflectional morphemes (plural -s and possessive 's), the Morphosyntactic Generation test (MorGen). Performance is averaged for each of the seven morphosyntactic targets independently, resulting in seven separate performance scores.

OUTCOMES & RESULTS

Individuals with PPA performed significantly more poorly than controls on the assessed morphemes in a repeated-measures analysis of variance, as well as on each morpheme considered independently via t-test.In a multivariable analysis of variance among PPA variants, the interaction of morpheme and PPA variant was significant, suggesting different variants produced the morphemes with a significantly different pattern of success. When morphemes were considered independently, only production of colour resulted in a significant difference between variants, driven by the performance of individuals with nfavPPA, who performed near-ceiling. When MorGen performance was used to predict PPA variant in a multinomial logistic regression the model was significant, with age, plural -s, noun, and number contributing significantly to the prediction. In a discriminate function analysis, classification of cases was best for agrammatic variant with 70% accuracy.

CONCLUSIONS

Individuals with PPA, particularly semantic and logopenic variants, demonstrated difficulty on the MorGen compared to controls. The MorGen proved useful in predicting PPA variant. These findings highlight the potential benefit of examining a broader range of morphemes, particularly bound morphemes and modifiers, in addition to the more frequently investigated classes of nouns and verbs when understanding PPA.

Part of Speech Production in Patients With Primary Progressive Aphasia: An Analysis Based on Natural Language Processing

Background Primary progressive aphasia (PPA) is a neurodegenerative disorder characterized by a progressive decline of language functions. Its symptoms are grouped into three PPA variants: nonfluent PPA, logopenic PPA, and semantic PPA. Grammatical deficiencies differ depending on the PPA variant. Aims This study aims to determine the differences between PPA variants with respect to part of speech (POS) production and to identify morphological markers that classify PPA variants using machine learning. By fulfilling these aims, the overarching goal is to provide objective measures that can facilitate clinical diagnosis, evaluation, and prognosis. Method and Procedure Connected speech productions from PPA patients produced in a picture description task were transcribed, and the POS class of each word was estimated using natural language processing, namely, POS tagging. We then implemented a twofold analysis: (a) linear regression to determine how patients with nonfluent PPA, semantic PPA, and logopenic PPA variants differ in their POS productions and (b) a supervised classification analysis based on POS using machine learning models (i.e., random forests, decision trees, and support vector machines) to subtype PPA variants and generate feature importance (FI). Outcome and Results Using an automated analysis of a short picture description task, this study showed that content versus function words can distinguish patients with nonfluent PPA, semantic PPA, and logopenic PPA variants. Verbs were less important as distinguishing features of patients with different PPA variants than earlier thought. Finally, the study showed that among the most important distinguishing features of PPA variants were elaborative speech elements, such as adjectives and adverbs.

Online sentence processing impairments in agrammatic and logopenic primary progressive aphasia: Evidence from ERP

Evidence from psycholinguistic research indicates that sentence processing is impaired in Primary Progressive Aphasia (PPA), and more so in individuals with agrammatic (PPA-G) than logopenic (PPA-L) subtypes. Studies have mostly focused on offline sentence production ability, reporting impaired production of verb morphology (e.g., tense, agreement) and verb-argument structure (VAS) in PPA-G, and mixed findings in PPA-L. However, little is known about real-time sentence comprehension in PPA. The present study is the first to compare real-time semantic, morphosyntactic and VAS processing in individuals with PPA (10 with PPA-G and 9 with PPA-L), and in two groups of healthy (22 young and 19 older) individuals, using event-related potentials (ERP). Participants were instructed to listen to sentences that were either well-formed (n = 150) or contained a violation of semantics (e.g., *Owen was mentoring pumpkins at the party, n = 50), morphosyntax (e.g., *The actors was singing in the theatre, n = 50) or VAS (*Ryan was devouring on the couch, n = 50), and were required to perform a sentence acceptability judgment task while EEG was recorded. Results indicated that in the semantic task both healthy and PPA groups showed an N400 response to semantic violations, which was delayed in PPA and older (vs. younger) groups. Morphosyntactic violations elicited a P600 in both groups of healthy individuals and in PPA-L, but not in PPA-G. A similar P600 response was also found only in healthy individuals for VAS violations; whereas, abnormal ERP responses were observed in both PPA groups, with PPA-G showing no evidence of VAS violation detection and PPA-L showing a delayed and abnormally-distributed positive component that was negatively associated with offline sentence comprehension scores. These findings support characterizations of sentence processing impairments in PPA-G, by providing online evidence that VAS and morphosyntactic processing are impaired, in the face of substantially preserved semantic processing. In addition, the results indicate that on-line processing of VAS information may also be impaired in PPA-L, despite their near-normal accuracy on standardized language tests of argument structure production.

Thematic Integration Impairments in Primary Progressive Aphasia: Evidence From Eye-Tracking

Primary progressive aphasia (PPA) is a degenerative disease affecting language while leaving other cognitive facilities relatively unscathed. The agrammatic subtype of PPA (PPA-G) is characterized by agrammatic language production with impaired comprehension of noncanonical filler-gap syntactic structures, such as object-relatives [e.g., The sandwich that the girl ate (gap) was tasty], in which the filler (the sandwich) is displaced from the object position within the relative clause to a position preceding both the verb and the agent (the girl) and is replaced by a gap linked with the filler. One hypothesis suggests that the observed deficits of these structures reflect impaired thematic integration, including impaired prediction of the thematic role of the filler and impaired thematic integration at the gap, but spared structure building (i.e., creation of the gap). In the current study, we examined the on-line comprehension of object-relative and subject-relative clauses in healthy controls and individuals with agrammatic and logopenic PPA using eye-tracking. Eye-movement patterns in canonical subject-relative clause structures were essentially spared in both PPA groups. In contrast, eye-movement patterns in noncanonical object-relative clauses revealed delayed thematic prediction in both agrammatic and logopenic PPA, on-time structure building (i.e., gap-filling) in both groups, and abnormal thematic integration in agrammatic, but not logopenic, PPA. We argue that these results are consistent with the hypothesis that agrammatic comprehension deficits reflect impaired thematic integration.

Language Breakdown in Primary Progressive Aphasias

Dementias with predominant language involvement, called primary progressive aphasias provide us with unique insight into systematic breakdown of language in neurodegenerative diseases and the structures and networks involved. Clinical and neuroimaging models quite distinct from those seen in stroke aphasias have evolved. In this short overview, we will discuss the cognitive processes involved in expressive and receptive verbal communication and how these processes are affected in the different variants of primary progressive aphasia producing distinctive clinical patterns. We will also discuss the brain's language network and how different components of the network break down in each of the primary progressive aphasia variants.

Quantifying grammatical impairments in primary progressive aphasia: Structured language tests and narrative language production

PURPOSE

This study examined grammatical production impairments in primary progressive aphasia (PPA), as measured by structured tests and narrative samples. We aimed to quantify the strength of the relationship between grammatical measures across tasks, and identify factors that condition it. Three grammatical domains were investigated: overall sentence production, verb morphology, and verb-argument structure.

METHODS

77 participants with PPA (34 PPA-G, 16 PPA-L, 15 PPA-S and 12 other) completed a battery of grammatical tests and a narrative language sample was obtained. Accuracy scores were computed for the language tests and the narrative samples were analyzed for both accuracy of selected narrative variables as well as grammatical diversity across the three grammatical domains. Principal components analysis (PCA) and multiple regression were used to examine cross-task relationships for all measures.

RESULTS

As expected on the basis of classification criteria, accuracy scores were lower for the PPA-G group as compared to the PPA-L and PPA-S participants for overall sentence production and verb morphology, but not argument structure. Grammatical accuracy in narratives strongly predicted overall language test performance in PPA-G, whereas grammatical diversity in narratives did so in PPA-L, and no significant correspondence between narrative and language test performance was found for PPA-S. For individuals with severe grammatical impairments only, error distribution for both morphology and argument structure was strongly associated in structured tasks and narratives.

CONCLUSIONS

Grammatical production in narrative language predicts accuracy elicited with structured language tests in PPA. However, unique narrative production patterns distinguish PPA by subtype: accuracy for PPA-G, and grammatical diversity for PPA-L. The impairment in PPA-G is likely to reflect a core impairment in grammar whereas that of PPA-L may be closely tied to the word retrieval and verbal working memory deficits that characterize this variant. This underscores the theoretical distinction between PPA-L and PPA-G, as well as the importance of including grammatical diversity measures in analyses of language production, especially for patients who do not display frank agrammatism. Further, the results suggest that measures of domain-specific language deficits (i.e., verb morphology vs. argument structure) are robust across tasks only in individuals with severe grammatical impairments.

Automated analysis of lexical features in Frontotemporal Degeneration

We implemented an automated analysis of lexical aspects of semi-structured speech produced by healthy elderly controls (n=37) and three patient groups with frontotemporal degeneration (FTD): behavioral variant FTD (n=74), semantic variant primary progressive aphasia (svPPA, n=42), and nonfluent/agrammatic PPA (naPPA, n=22). Based on previous findings, we hypothesized that the three patient groups and controls would differ in the counts of part-of-speech (POS) categories and several lexical measures. With a natural language processing program, we automatically tagged POS categories of all words produced during a picture description task. We further counted the number of wh -words, and we rated nouns for abstractness, ambiguity, frequency, familiarity, and age of acquisition. We also computed the cross-entropy estimation, which is a measure of word predictability, and lexical diversity for each description. We validated a subset of the POS data that were automatically tagged with the Google Universal POS scheme using gold-standard POS data tagged by a linguist, and we found that the POS categories from our automated methods were more than 90% accurate. For svPPA patients, we found fewer unique nouns than in naPPA and more pronouns and wh -words than in the other groups. We also found high abstractness, ambiguity, frequency, and familiarity for nouns and the lowest cross-entropy estimation among all groups. These measures were associated with cortical thinning in the left temporal lobe. In naPPA patients, we found increased speech errors and partial words compared to controls, and these impairments were associated with cortical thinning in the left middle frontal gyrus. bvFTD patients' adjective production was decreased compared to controls and was correlated with their apathy scores. Their adjective production was associated with cortical thinning in the dorsolateral frontal and orbitofrontal gyri. Our results demonstrate distinct language profiles in subgroups of FTD patients and validate our automated method of analyzing FTD patients' speech.

Progressive agrammatic aphasia without apraxia of speech as a distinct syndrome

Agrammatic aphasia affects grammatical language production and can result from a neurodegenerative disease. Although it typically presents with concomitant apraxia of speech, this is not always the case. Little is known about the clinical course and imaging features of patients that present with agrammatism in the absence of apraxia of speech, which we will refer to as progressive agrammatic aphasia. We aimed to make a detailed description of the longitudinal clinical, linguistic, and neuroimaging features of a cohort of 11 patients with progressive agrammatic aphasia to provide a complete picture of this syndrome. All patients underwent detailed speech and language, neurological and neuropsychological assessments, 3 T structural and diffusion tensor imaging MRI, 18F-fluorodeoxyglucose and Pittsburgh compound B PET. The 11 patients were matched by age and gender to 22 patients who had mixed apraxia of speech and agrammatism. The progressive agrammatic aphasia patients performed abnormally on tests of language, general cognition, executive function, and functional ability at baseline and declined in these measures over time. Only two patients eventually developed apraxia of speech, while parkinsonism was absent-to-mild throughout all visits for all patients. When compared to the patients with mixed apraxia of speech and agrammatism, the patients with progressive agrammatic aphasia performed better on tests of motor speech and parkinsonism but more poorly, and declined faster over time, on tests of general aphasia severity, agrammatism, and naming. The patients with progressive agrammatic aphasia also showed different neuroimaging abnormalities, with greater atrophy, hypometabolism and white matter tract degeneration in the prefrontal and anterior temporal lobes compared to patients with mixed apraxia of speech and agrammatism. These differences were more pronounced as the disease progressed. These results demonstrate that progressive agrammatic aphasia has a different clinical disease course and different underlying neuroanatomical abnormalities than patients with the more common syndrome of mixed agrammatism and apraxia of speech. This supports the distinction of progressive agrammatic aphasia and has implications for the classification of patients with agrammatic aphasia.

Grammatical Ability Predicts Relative Action Naming Impairment in Primary Progressive Aphasia

BACKGROUND

Findings from several studies have indicated that participants with nfvPPA and participants with svPPA exhibit different patterns on action and object naming tasks, while other recent studies have found that neither participants with nfvPPA nor participants with svPPA show a significant difference in accuracy between object naming and action naming.

AIMS

The goal of this study was to test the hypothesis that relative action naming impairment is associated with grammatical ability in PPA, rather than a specific subtype of PPA.

METHODS & PROCEDURES

Thirty-four participants with PPA completed the Boston Naming Test, the Action Naming subtest of the Boston Diagnostic Aphasia Examination, and the Northwestern Anagram Test, which was used to measure grammatical ability. Z-scores for the two naming tasks were calculated based on normative data from unimpaired controls. For each participant with PPA, the relative action naming impairment was calculated by subtracting the object naming z-score from the action naming z-score. Linear regression analysis was then used to evaluate the role of grammatical ability as a predictor of relative action naming impairment, while controlling for age, education, cognitive ability (as measured by the Montreal Cognitive Assessment), and semantic ability (as measured by the Pyramids and Palm Trees test). The interaction between grammatical ability and each control variable was also examined.

OUTCOMES & RESULTS

The main effect of grammatical ability was a significant predictor of relative action naming impairment, while none of the control variables was a significant predictor. However, the interaction between grammatical ability and semantic ability was also significant.

CONCLUSIONS

Individuals who have both grammatical impairment and semantic impairment have the largest relative action naming impairment. These individuals may benefit from a treatment that focuses on the retrieval of verbs and their arguments.

Northwestern Anagram Test-Italian (Nat-I) for primary progressive aphasia

OBJECTIVES

To test the ability of the Northwestern Anagram Test-Italian (NAT-I) to distinguish between the non-fluent/agrammatic (nfv-) and phonological/logopenic (lv-) variants of primary progressive aphasia (PPA), and to determine the relationship between NAT-I variables and brain integrity in PPA patients.

METHODS

13 nfvPPA and 8 lvPPA patients underwent the 44-item-version of NAT-I and brain MRI. The NAT-I was also administered to six patients with the semantic variant (sv) PPA to sample performance in cases with no grammatical deficits. Performances were recorded and compared between patient groups. Receiver Operating Characteristic curve analysis assessed the ability of NAT-I to discriminate nfvPPA and lvPPA. The correlation between anatomical changes and NAT-I variables were assessed. A shortened (22-item)-version of NAT-I was also tested for classification ability.

RESULTS

Participants with NfvPPA performed more poorly than lvPPA patients on canonical and non-canonical sentences. NAT-I non-canonical sentence and total scores achieved the highest diagnostic accuracy in discriminating the two patient groups (area under the curve: .93 and .91, respectively). SvPPA participants showed performances similar to lvPPA. NAT-I variables correlated with the integrity of the left inferior frontal gyrus and the body of the corpus callosum. The NAT-I 22-item-version total and non-canonical sentences scores reached diagnostic accuracy comparable to the full version.

CONCLUSIONS

The NAT-I, in particular the measure of non-canonical syntax, is an effective tool for distinguishing nfvPPA and lvPPA patients and correlated with the integrity of crucial brain regions implicated in syntactic processing. The 22-item-brief version of NAT-I is suitable for clinical practice and research.

Verb-argument integration in primary progressive aphasia: Real-time argument access and selection

BACKGROUND

Impaired sentence comprehension is observed in the three major subtypes of PPA, with distinct performance patterns relating to impairments in comprehending complex sentences in the agrammatic (PPA-G) and logopenic (PPA-L) variants and word comprehension in the semantic subtype (PPA-S). However, little is known about basic combinatory processes during sentence comprehension in PPA, such the integration of verbs with their subject and object(s) (verb-argument integration).

METHODS

The present study used visual-world eye-tracking to examine real-time verb-argument integration in individuals with PPA (12 with PPA-G, 10 with PPA-L, and 6 with PPA-S) and neurotypical older adults (15). Two baseline experiments probed eye movement control, using a non-linguistic task, and noun comprehension, respectively. Two verb-argument integration experiments examined the effects of verb meaning on (a) lexical access of the verb's direct object (argument access) and (b) selection of a semantically-appropriate direct object (argument selection), respectively. Eye movement analyses were conducted only for trials with correct behavioral responses, allowing us to distinguish accuracy and online processing.

RESULTS

The eye movement control experiment revealed no significant impairments in PPA, whereas the noun comprehension experiment revealed reduced accuracy and eye-movement latencies in PPA-S, and to a lesser extent PPA-G. In the argument access experiment, verb meaning facilitated argument access normally in PPA-G and PPA-L; in PPA-S, verb-meaning effects emerged on an atypical time course. In the argument selection experiment, significant impairments in accuracy were observed only in PPA-G, accompanied by markedly atypical eye movement patterns.

CONCLUSION

This study revealed two distinct patterns of impaired verb-argument integration in PPA. In PPA-S, impaired verb-argument integration was observed in the argument access experiment, indicating impairments in basic semantic combinatory processes which likely relate to damage in ventral language pathways. In contrast, listeners with PPA-G showed marked impairments of argument selection, likely relating to damage to left inferior frontal regions.

Primary progressive aphasia: a model for neurodegenerative disease

PURPOSE OF REVIEW

Knowledge on primary progressive aphasia (PPA) has expanded rapidly in the past few decades. Clinical characteristics, neuroimaging correlates, and neuropathological features of PPA are better delineated. This facilitates scientific studies on the disease pathophysiology and allows speech and language therapy to be more precisely targeted. This review article begins with a summary of the current understanding of PPA and discusses how PPA can serve as a model to promote scientific discovery in neurodegenerative diseases.

RECENT FINDINGS

Studies on the different variants of PPA have demonstrated the high compatibility between clinical presentations and neuroimaging features, and in turn, enhances the understanding of speech and language neuroanatomy. In addition to the traditional approach of lesion-based or voxel-based mapping, scientists have also adopted functional connectivity and network topology approaches that permits a more multidimensional understanding of neuroanatomy. As a result, pharmacological and cognitive therapeutic strategies can now be better targeted towards specific pathological/molecular and cognitive subtypes.

SUMMARY

Recent scientific advancement in PPA potentiates it to be an optimal model for studying brain network vulnerability, neurodevelopment influences and the effects of nonpharmacological intervention in neurodegenerative diseases.

Quantitative assessment of grammar in amyloid-negative logopenic aphasia

Logopenic primary progressive aphasia (lvPPA) typically results from underlying Alzheimer's disease, but subjects have been reported that do not show beta-amyloid (Aβ) deposition. These subjects do not differ on neurological and speech-language testing from Aβ-positive lvPPA, but they impressionistically show increased grammatical deficits. We performed a quantitative linguistic analysis of grammatical characteristics in Aβ-negative lvPPA compared to Aβ-positive lvPPA and agrammatic PPA, which is characterized by increased grammatical difficulties. Aβ-negative lvPPA used fewer function words and correct verbs but more syntactic and semantic errors compared to Aβ-positive lvPPA. These measures did not differ between Aβ-negative lvPPA and agPPA. Both lvPPA cohorts showed a higher mean length of utterance, more complex sentences, and fewer nouns than agPPA. Aβ-negative lvPPA subjects appear unique and share linguistic features with both agPPA and Aβ-positive lvPPA. Quantitative language analysis in lvPPA may be able to distinguish those with and without Aβ deposition.

The Role of Language Severity and Education in Explaining Performance on Object and Action Naming in Primary Progressive Aphasia

Despite the common assumption that atrophy in a certain brain area would compromise the function that it subserves, this is not always the case, especially in complex clinical syndromes such as primary progressive aphasia (PPA). Clinical and demographic information may contribute to PPA phenotypes and explain the manifested impairments better than atrophy. In the present study, we asked how much variance of the object and action naming impairments observed in PPA may be attributed to atrophy in the language network alone vs. additional clinical and demographic factors including language severity and education. Thirty-nine participants with PPA underwent magnetic resonance imaging (MRI) for volumetric analysis and a complete neuropsychological examination, including standardized tests of object and action naming. We used stepwise regression models to compare atrophy (volumetric model) to clinical/demographic variables (clinical-demographic model) for naming objects and actions. The clinical-demographic model was the best-fit model that explained the largest amount of variance in both object and action naming. Brain volume measurements alone explained little variance in both object and action naming. Clinical factors, particularly language severity, and demographic factors, particularly education, need to be considered in conjunction with brain volumes in PPA. The present study emphasizes the complexity of PPA as a syndrome and provides an example of how volumetric, clinical and demographic factors may interact in determining naming performance/deterioration.

Quantitative Analysis of Agrammatism in Agrammatic Primary Progressive Aphasia and Dominant Apraxia of Speech

PURPOSE

The aims of the study were to assess and compare grammatical deficits in written and spoken language production in subjects with agrammatic primary progressive aphasia (agPPA) and in subjects with agrammatism in the context of dominant apraxia of speech (DAOS) and to investigate neuroanatomical correlates.

METHOD

Eight agPPA and 21 DAOS subjects performed the picture description task of the Western Aphasia Battery (WAB) both in writing and orally. Responses were transcribed and coded for linguistic analysis. agPPA and DAOS were compared to 13 subjects with primary progressive apraxia of speech (PPAOS) who did not have agrammatism. Spearman correlations were performed between the written and spoken variables. Patterns of atrophy in each group were compared, and relationships between the different linguistic measures and integrity of Broca's area were assessed.

RESULTS

agPPA and DAOS both showed lower mean length of utterance, fewer grammatical utterances, more nonutterances, more syntactic and semantic errors, and fewer complex utterances than PPAOS in writing and speech, as well as fewer correct verbs and nouns in speech. Only verb ratio and proportion of grammatical utterances correlated between modalities. agPPA and DAOS both showed greater involvement of Broca's area than PPAOS, and atrophy of Broca's area correlated with proportion of grammatical and ungrammatical utterances and semantic errors in writing and speech.

CONCLUSIONS

agPPA and DAOS subjects showed similar patterns of agrammatism, although subjects performed differently when speaking versus writing. Integrity of Broca's area correlates with agrammatism.

Clinical, Anatomical, and Pathological Features in the Three Variants of Primary Progressive Aphasia: A Review

Primary progressive aphasias (PPA) are neurodegenerative diseases clinically characterized by an early and relatively isolated language impairment. Three main clinical variants, namely the nonfluent/agrammatic variant (nfvPPA), the semantic variant (svPPA), and the logopenic variant (lvPPA) have been described, each with specific linguistic/cognitive deficits, corresponding anatomical and most probable pathological features. Since the discovery and the development of diagnostic criteria for the PPA variants by the experts in the field, significant progress has been made in the understanding of these diseases. This review aims to provide an overview of the literature on each of the PPA variant in terms of their clinical, anatomical and pathological features, with a specific focus on recent findings. In terms of clinical advancements, recent studies have allowed a better characterization and differentiation of PPA patients based on both their linguistic and non-linguistic profiles. In terms of neuroimaging, techniques such as diffusion imaging and resting-state fMRI have allowed a deeper understanding of the impact of PPA on structural and functional connectivity alterations beyond the well-defined pattern of regional gray matter atrophy. Finally, in terms of pathology, despite significant advances, clinico-pathological correspondence in PPA remains far from absolute. Nonetheless, the improved characterization of PPA has the potential to have a positive impact on the management of patients. Improved reliability of diagnoses and the development of reliable in vivo biomarkers for underlying neuropathology will also be increasingly important in the future as trials for etiology-specific treatments become available.

Neuropsychological differentiation of progressive aphasic disorders

The differentiation of subtypes of primary progressive aphasia (PPA) remains challenging. We aimed to identify optimum neuropsychological measures for characterizing PPA, to examine the relationship between behavioural change and subtypes of PPA and to determine whether characteristic profiles of language, working memory, and behavioural changes occur in PPA. Forty‐seven patients with PPA and multi‐domain Alzheimer's disease (AD) together with 19 age‐matched controls underwent a large battery of working memory and language tests. We found that simple tasks of sentence ordering, narrative production, and buccofacial praxis were particularly useful in differentiating non‐fluent/agrammatic variant PPA (nfvPPA) from other PPA subtypes, whereas a test of single word comprehension was useful in detecting semantic dementia (SD). No individual tests were discriminating for logopenic variant PPA (lvPPA) relative to nfvPPA. LvPPA and multidomain AD exhibited similar language profiles. A principal components analysis revealed that characteristic PPA profiles extended beyond the realms of language, in particular, the presence of apraxia in nfvPPA, behavioural changes in SD, and working memory deficits in lvPPA. These findings suggest that not all tests are equally discriminatory for PPA and highlight the importance of a test profile in differentiating PPA. These results also support the view that lvPPA is a focal form of AD and emphasize the difficulties classifying lvPPA.

Connected Language in Late Middle-Aged Adults at Risk for Alzheimer's Disease

Connected language is often impaired among people with Alzheimer's disease (AD), yet little is known about when language difficulties first emerge on the path to a clinical diagnosis. The objective of this study was to determine whether individuals with psychometric (preclinical) evidence of amnestic mild cognitive impairment (pMCI) showed deficits in connected language measures. Participants were 39 pMCI and 39 cognitively healthy (CH) adults drawn from the Wisconsin Registry for Alzheimer's Prevention, who were matched for age, literacy, and sex. Participants completed a connected language task in which they described the Cookie Theft picture from the Boston Diagnostic Aphasia Examination. Language samples were analyzed across three language domains: content, syntactic complexity, and speech fluency. Paired t-tests were used to compare CH and pMCI groups on all variables, and Cohen's d effect sizes were calculated for each comparison. The CH and pMCI groups differed significantly on measures of content (e.g., CH group produced more semantic units, more unique words and had larger idea density, on average, than the pMCI group). The picture description findings are consistent with previous retrospective studies showing semantic language differences in adults with autopsy-confirmed AD. Given that these comparisons are between cognitively healthy and pMCI individuals (before a clinical MCI diagnosis), these findings may represent subtle language difficulty in spontaneous speech, and may be predictive of larger language changes over time.

SAND: a Screening for Aphasia in NeuroDegeneration. Development and normative data

Language assessment has a critical role in the clinical diagnosis of neurodegenerative diseases, in particular, in the case of Primary Progressive Aphasia (PPA). The current diagnostic criteria (Gorno-Tempini et al., 2011) identify three main variants on the basis of clinical features and patterns of brain atrophy. Widely accepted tools to diagnose, clinically classify, and follow up the heterogeneous language profiles of PPA are still lacking. In this study, we develop a screening battery, composed of nine tests (picture naming, word and sentence comprehension, word and sentence repetition, reading, semantic association, writing and picture description), following the recommendations of current diagnostic guidelines and taking into account recent research on the topic. All tasks were developed with consideration of the psycholinguistic factors that can affect performance, with the aim of achieving sensitivity to the language deficit to which each task was relevant, and to allow identification of the selective characteristic impairments of each PPA variant. Normative data on 134 Italian subjects pooled across homogeneous subgroups for age, sex, and education are reported. Although further work is still needed, this battery represents a first step towards a concise multilingual standard language examination, a fast and simple tool to help clinicians and researchers in the diagnosis of PPA.

Tracking the development of agrammatic aphasia: A tensor-based morphometry study

Agrammatic aphasia can be observed in neurodegenerative disorders and has been traditionally linked with damage to Broca's area, although there have been disagreements concerning whether damage to Broca's area is necessary or sufficient for the development of agrammatism. We aimed to investigate the neuroanatomical correlates of the emergence of agrammatic aphasia utilizing a unique cohort of patients with primary progressive apraxia of speech (PPAOS) that did not have agrammatism at baseline but developed agrammatic aphasia over time. Twenty PPAOS patients were recruited and underwent detailed speech/language assessments and 3T MRI at two visits, approximately two years apart. None of the patients showed evidence of agrammatism in writing or speech at baseline. Eight patients developed aphasia at follow-up (progressors) and 12 did not (non-progressors). Tensor-based morphometry utilizing symmetric normalization (SyN) was used to assess patterns of grey matter atrophy and voxel-based morphometry was used to assess patterns of grey matter loss at baseline. The progressors were younger at onset and more likely to show distorted sound substitutions or additions compared to non-progressors. Both groups showed change over time in premotor and motor cortices, posterior frontal lobe, basal ganglia, thalamus and midbrain, but the progressors showed greater rates of atrophy in left pars triangularis, thalamus and putamen compared to non-progressors. The progressors also showed greater grey matter loss in pars triangularis and putamen at baseline. This cohort provided a unique opportunity to assess the anatomical changes that accompany the development of agrammatic aphasia. The results suggest that damage to a network of regions including Broca's area, thalamus and basal ganglia are responsible for the development of agrammatic aphasia in PPAOS. Clinical and neuroimaging abnormalities were also present before the onset of agrammatism that could help improve prognosis in these subjects.

Lack of Frank Agrammatism in the Nonfluent Agrammatic Variant of Primary Progressive Aphasia

Background/Aims

Frank agrammatism, defined as the omission and/or substitution of grammatical morphemes with associated grammatical errors, is variably reported in patients with nonfluent variant primary progressive aphasia (nfPPA). This study addressed whether frank agrammatism is typical in agrammatic nfPPA patients when this feature is not required for diagnosis.

Method

We assessed grammatical production in 9 patients who satisfied current diagnostic criteria. Although the focus was agrammatism, motor speech skills were also evaluated to determine whether dysfluency arose primarily from apraxia of speech (AOS), instead of, or in addition to, agrammatism. Volumetric MRI analyses provided impartial imaging-supported diagnosis.

Results

The majority of cases exhibited neither frank agrammatism nor AOS.

Conclusion

There are nfPPA patients with imaging-supported diagnosis and preserved motor speech skills who do not exhibit frank agrammatism, and this may persist beyond the earliest stages of the illness. Because absence of frank agrammatism is a subsidiary diagnostic feature in the logopenic variant of PPA, this result has implications for differentiation of the nonfluent and logopenic variants, and indicates that PPA patients with nonfluent speech in the absence of frank agrammatism or AOS do not necessarily have the logopenic variant.

Supporting communication for patients with neurodegenerative disease

BACKGROUND

Communication supports, referred to as augmentative and alternative communication (AAC), are an integral part of medical speech-language pathology practice, yet many providers remain unfamiliar with assessment and intervention principles. For patients with complex communication impairments secondary to neurodegenerative disease, AAC services differ depending on whether their condition primarily affects speech and motor skills (ALS), language (primary progressive aphasia) or cognition (Alzheimer's disease). This review discusses symptom management for these three conditions, identifying behavioral strategies, low- and high-tech solutions for implementation during the natural course of disease. These AAC principles apply to all neurodegenerative diseases in which common symptoms appear.

OBJECTIVES

To present AAC interventions for patients with neurodegenerative diseases affecting speech, motor, language and cognitive domains. Three themes emerge: (1) timing of intervention: early referral, regular re-evaluations and continual treatment are essential; (2) communication partners must be included from the onset to establish AAC acceptance and use; and (3) strategies will change over time and use multiple modalities to capitalize on patients' strengths.

CONCLUSIONS

AAC should be standard practice for adults with neurodegenerative disease. Patients can maintain effective, functional communication with AAC supports. Individualized communication systems can be implemented ensuring patients remain active participants in daily activities.

Primary progressive aphasia and the evolving neurology of the language network

Primary progressive aphasia (PPA) is caused by selective neurodegeneration of the language-dominant cerebral hemisphere; a language deficit initially arises as the only consequential impairment and remains predominant throughout most of the course of the disease. Agrammatic, logopenic and semantic subtypes, each reflecting a characteristic pattern of language impairment and corresponding anatomical distribution of cortical atrophy, represent the most frequent presentations of PPA. Such associations between clinical features and the sites of atrophy have provided new insights into the neurology of fluency, grammar, word retrieval, and word comprehension, and have necessitated modification of concepts related to the functions of the anterior temporal lobe and Wernicke's area. The underlying neuropathology of PPA is, most commonly, frontotemporal lobar degeneration in the agrammatic and semantic forms, and Alzheimer disease (AD) pathology in the logopenic form; the AD pathology often displays atypical and asymmetrical anatomical features consistent with the aphasic phenotype. The PPA syndrome reflects complex interactions between disease-specific neuropathological features and patient-specific vulnerability. A better understanding of these interactions might help us to elucidate the biology of the language network and the principles of selective vulnerability in neurodegenerative diseases. We review these aspects of PPA, focusing on advances in our understanding of the clinical features and neuropathology of PPA and what they have taught us about the neural substrates of the language network.